What is this map, and how would I use it?
It looks like a regular normal map to me, which is used to add texture to a surface without changing the actual geometry. A normal map contains surface angle information, and a bump map contains surface height information.

Here is a good article on normal maps: https://cgcookie.com/articles/normal-vs-displacement-mapping-why-games-use-normals

And here is a screenshot of a simple node setup for a normal map and what it looks like rendered on a simple plane with a point light in Eevee. I hope this helps!